BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention relates to a rotational angle detecting device, and, more particularly,
to a rotational angle detecting device which is connected to a rotary member, such
as a steering shaft of an automobile, and which outputs two or more detection signals
which are in correspondence with the rotational angle and the rotational direction
of the steering wheel in order to detect the rotational angle of the rotary member
using these detection signals.
2. Description of the Related Art
[0002] Hitherto, a rotary sensor has been used to form a rotation detecting section. As
an example of such a rotary sensor, the following rotary sensor has been proposed.
(This rotary sensor will hereinafter be referred to as "proposed rotary sensor.")
[0003] The proposed rotary sensor comprises a fixed base member, a rotor which can rotate
with respect to the base member, and a rotation detecting section disposed between
the base member and the rotor. The rotation detecting section outputs a sinusoidal
first detection signal, a sinusoidal second detection signal, and a third detection
signal. The first and second detection signals have constant amplitudes and the same
periods, and are out of phase by 1/4 wavelength. The third detection signal has the
same period in the entire rotational range of the rotor and increases linearly. When
the rotary sensor is used, the rotor is connected to a rotary member such as a steering
shaft of an automobile. Here, the rotation detecting section comprises first and second
magnets, and first to third Hall elements. The first and second magnets are disposed
at the base member. The first and second Hall elements are disposed at the rotor so
as to oppose the first magnet at an angle of substantially 90 degrees. The third Hall
element is disposed so as to oppose the second magnet.
[0004] In this structure, when the steering wheel is rotated in order to rotate the steering
shaft connected to the steering wheel, the rotor connected to the steering shaft rotates,
causing the rotation detecting section to generate the first to third detection signals
which are in correspondence with the rotational angle and the rotational direction
of the steering shaft.
[0005] The generated first to third detection signals are supplied to a controlling section
installed in the automobile. Based on the supplied third detection signal, the controlling
section detects the rotational direction and the rough rotational angle from the neutral
position of the steering wheel (or the steering shaft). Similarly, based on the supplied
first and second detection signals, the controlling section detects the very small
rotational angle from the neutral position of the steering wheel (or the steering
shaft). The detected rotational direction and rotational angles from the neutral position
of the steering wheel (or the steering shaft) are supplied to a controller as detection
information. Based on the supplied detection information, the controller carefully
controls the traction and the suspension of the automobile.
[0006] Fig. 7 is a graph showing the relationship between the angle of rotation of the steering
wheel and the output voltage of each of the first, second, and third detection signals.
[0007] In Fig. 7., reference numeral 71 denotes the first detection signal, reference numeral
72 denotes the second detection signal, and reference numeral 73 denotes the third
detection signal. Fig. 7 shows the variations in the output voltages of the first
to third detection signals 71 to 73 with respect to a rotational angle of zero degrees
(that is, the neutral position) of the steering wheel, within a rotational angle range
of from 0° to +225°.
[0008] Here, the first detection signal 71 and the second detection signal 72 are sinusoidal,
have the same amplitudes and periods, and are out of phase by 1/4 wavelength. For
both of these signals 71 and 72, the voltages are 4.5 V at maximum amplitude, and
0.5 V at minimum amplitude. For the first detection signal 71, when the rotational
angles are +67.5° and +157.5°, the amplitude thereof is a minimum (voltage = 0.5 V).
For the second detection signal 72, when the rotational angles are 0°, +90.0°, and
+180.0°, the amplitude thereof is a minimum (voltage = 0.5 V). The third detection
signal increases linearly from a rotational angle of 0° to +225°, and has a voltage
of 2.5 V when the rotational angle is 0° and a voltage of 3.0 V when the rotational
angle is +180°.
[0009] Hereunder, using the graph of Fig. 7, the detection of the rotational direction and
rotational angle of the steering wheel carried out at the controlling section will
be described.
[0010] First, when the controlling section is to detect the rotational direction of the
steering wheel from the neutral position (which corresponds to an angle of rotation
of 0°) of the steering wheel, it detects the rotational direction by the voltage value
of the supplied third detection signal 73 which has been supplied. More specifically,
when the voltage value of the third detection signal 73 is more than 2.5 V, the controlling
section detects that the rotational direction of the steering wheel corresponds to
one direction (that is, the positive rotational angle direction). On the other hand,
when the voltage value of the third detection signal 73 is less than 2.5 V, the controlling
section detects that the rotational direction of the steering wheel corresponds to
the other direction (that is, the negative rotational angle direction).
[0011] Then, as shown in Fig. 7, the controlling section divides the entire rotational angle
range of the steering wheel, such as a rotational angle range of 1440° (±720°), into
angle (such as 90°) divisions which correspond to one wavelength of each of the first
detection signal 71 and the second detection signal 72. These divisions are represented
as ..., N - 1, N, N - 2, ... Then, based on the voltage value of the supplied third
detection signal 73, the controlling section detects a rough rotational angle which
indicates to which angle division the rotational angle of the steering wheel corresponds.
For example, if the controlling section detects that the voltage value of the third
detection signal 73 is 2.8 V, the angle division N is detected as the angle division
corresponding to this voltage value.
[0012] Thereafter, the controlling section determines a first voltage value V
1 and a second voltage value V
2 when the voltage values of the supplied first and second detection signals 71 and
72 are the same in the detected angle division N. Using the obtained first and second
voltage values V
1 and V
2, one detection signal which has a voltage value outside the voltage range of the
first and second voltage values V
1 and V
2, and the other detection signal which has a voltage value within the voltage range
of the first and second voltage values V
1 and V
2 are determined.
[0013] After the determination, the controlling section determines whether the other detection
signal whose voltage value lies within the voltage range of the first and second voltage
values V
1 and V
2 is the first detection signal 71 or the second detection signal 72. At the same time,
the controlling section determines whether the one detection signal whose voltage
value lies outside the voltage range of the first and second voltage values V
1 and V
2 has a voltage value which is less than the first voltage value V
1 or greater than the second voltage value V
2, and whether the other detection signal whose voltage value lies within the voltage
range of the first and second voltage values V
1 and V
2 exists in any one of four division portions of the one angle division N, that is,
in any one of first to fourth angle division portions H1 to H4 of the one angle division
N. Accordingly, by finding out whether the other detection signal exists in any one
of the first to fourth angle division portions H1 to H4 of the one angle section N,
the controlling section detects the very small rotational angle of the steering wheel.
[0014] Here, for the other detection signal whose voltage value lies within the voltage
range of the first and second voltage values V
1 and V
2, the first angle division portion H1 corresponds to a rising (inclined) portion 71U
where the first detection signal 71 rises linearly, the second angle division portion
H2 corresponds to a rising (tilted) portion 72U where the second detection signal
72 rises linearly, the third angle division portion H3 corresponds to a falling (inclined)
portion 71D where the first detection signal 71 falls linearly, and the fourth angle
division portion H4 corresponds to a falling (inclined) portion 72D where the second
detection signal 72 falls linearly.
[0015] In the proposed rotational angle detecting device having the rotary sensor (that
is, the rotation detecting section), as the rotary member (or rotor) rotates, the
first to third detection signals are output from the rotation detecting section. When
the controlling section detects the rotational direction and rotational angle of the
rotary member based on the supplied first to third detection signals, the controlling
section detects the rotational direction and the rough rotational angle of the rotary
member based on the amplitude (that is, the voltage value) of the third detection
signal. In addition, the controlling section detects the very small rotational angle
of the rotary member based on the linearly inclined portions of the first and second
detection signals. Therefore, the rotational angles and rotational direction of the
rotary member can be detected with high precision over wide ranges thereof.
[0016] However, in the proposed rotational angle detecting device having the rotation detecting
section, the first to third detection signals which are output from the rotation detecting
section are used as they are to detect the rotational angles and rotational direction
of the rotary member. Therefore, if for any reason a detection signal is erroneously
output from the rotation detecting section, a rotational angle and rotational direction
corresponding to the content of the erroneously output detection signal is detected.
Consequently, erroneous angle detection information is supplied to the controller
from the controlling section, so that the controller may not properly control the
traction and the suspension of the automobile.
SUMMARY OF THE INVENTION
[0017] In view of the above-described problems, it is an object of the present invention
to provide a highly reliable rotational angle detecting device which can perform a
required controlling operation using a detection signal which has been determined
as being a proper detection signal by a controlling section which determines whether
or not various detection signals output from a rotation detecting section are proper
detection signals.
[0018] To this end, according to a first aspect of the present invention, there is provided
rotational angle detecting device comprising a rotor connected to a rotary member;
a rotation detecting section for outputting a sinusoidal first detection signal and
a sinusoidal second detection signal as a result of the rotation of the rotor, the
first detection signal and the second detection signal having constant amplitudes,
having the same periods, and having wavelengths which are out of phase; a storage
section for updating and storing the first detection signal and the second detection
signal; and a controlling section. In the rotational angle detecting device, the controlling
section compares a most recent first detection signal and a most recent second detection
signal output by the rotation detecting section, and determines whether or not either
one of the most recent first and second detection signals falls within a proper range
with respect to the other of the most recent first and second detection signals. When
the controlling section determines that either one of the first and second detection
signals falls within the proper range, the controlling section supplies the most recent
first and second detection signals to a controller. On the other hand, when the controlling
section determines that either one of the most recent first and second detection signals
falls outside the proper range with respect to the other of the most recent first
and second detection signals, the controlling section does not supply the most recent
first and second detection signals to the controller.
[0019] In the first structure, the first and second detection signals output from the rotation
detecting section are sent to the storage section, are updated, and are stored in
the storage section. The controlling section cyclically compares the most recent first
and second detection signals output from the rotation detecting section in a determined
period. When the controlling section determines that at least one of the most recent
first and second detection signals is an unsuitable detection signal, the angle signal
based on the unsuitable detection signal is not supplied to the controller. Therefore,
an improper piece of detection information which is created based on the unsuitable
detection signal is not supplied to the controller, thereby allowing a suitable controlling
operation to be performed at all times to operate a fail safe structure by the controller.
Consequently, it is possible to provide a highly reliable rotational angle detecting
device.
[0020] According to a second aspect of the present invention, there is provided a rotational
angle detecting device comprising a rotor connected to a rotary member; a rotation
detecting section for outputting a sinusoidal first detection signal, a sinusoidal
second detection signal, and a third detection signal, the first detection signal
and the second detection signal having constant amplitudes, having the same periods,
and having wavelengths which are out of phase, and the third detection signal increasing
linearly over an entire rotational range of the rotary member; a storage section for
updating and storing therein the first detection signal, the second detection signal,
and the third detection signal; and a controlling section. In the rotational angle
detecting device, the controlling section compares a most recent first detection signal
and a most recent second detection signal output from the rotation detecting section,
and determines whether or not either one of the most recent first and second detection
signals falls within a proper range with respect to the other of the most recent first
and second detection signals. When the controlling section determines that either
one of the most recent first and second detection signals falls within the proper
range, the controlling section compares a most recent third detection signal with
the most recent first and second detection signals. When the controlling section determines
that the signals fall within proper ranges, the controlling section supplies the most
recent first to third detection signals to a controller, whereas, when the controlling
section determines that the signals fall outside the proper ranges, the controlling
section supplies to the controller the third detection signal previously stored in
the storage section and the most recent first and second detection signals.
[0021] In the second structure, the first to third detection signals output from the rotation
detecting section are sent to the storage section, are updated, and are stored in
the storage section. The controlling section, first, cyclically compares the most
recent first and second detection signals output from the rotation detecting section
in a determined period. When the controlling section determines that both of the most
recent first and second detection signals are suitable detection signals, the controlling
section cyclically compares the most recent third detection signal output from the
rotation detecting section with the most recent first and second detection signals
in a similarly determined period. When the controlling section determines that the
third detection signal is an unsuitable detection signal, it creates a proper piece
of detection information using the most recent first and second detection signals
and the immediately previously obtained third detection signal read out from the storage
section, and the detection information is supplied to the controller. Therefore, an
improper piece of detection information which is created based on any unsuitable detection
signal is no longer supplied to the controller, thereby allowing a proper controlling
operation to be carried out at all times to operate a fail safe structure by the controller.
Consequently, using the detection information based on the first to third detection
signals, it is possible to provide a rotational angle detecting device which is more
reliable than the rotational angle detecting device having the first structure.
[0022] The rotary member may be a steering shaft of an automobile, and the first detection
signal and the second detection signal, or the first detection signal to the third
detection signal may be steering angle detection signals of the steering shaft.
[0023] By virtue of this structure, it is possible to provide a highly reliable rotational
angle detecting device for generating detection signals of the steering angle of a
steering shaft of an automobile.
[0024] The steering angle detection signals may be supplied to the controller through a
local area network bus line provided in the automobile.
[0025] By virtue of this structure, it is possible to provide a highly reliable rotational
angle detecting device for properly performing various automobile controlling operations
as a result of generating detection signals of the steering angle of a steering shaft
of an automobile.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Fig. 1 is a structural view showing the main portion of an embodiment of a rotational
angle detecting device in accordance with the present invention.
[0027] Figs. 2A and 2B are sectional views showing in detail the structure of a rotary sensor
which forms a rotation detecting section used in the present invention.
[0028] Fig. 3 is a graph showing the waveforms of first and second detection signals in
the rotary sensor shown in Fig. 2 which are output when a steering wheel is rotating.
[0029] Fig. 4 is a graph showing the waveform of a third detection signal in the rotary
sensor shown in Fig. 2 which is output when the steering wheel is rotating.
[0030] Fig. 5 is a graph showing the waveforms of the first to third detection signals in
the rotary sensor shown in Fig. 2 which are output when the steering wheel is rotating.
[0031] Fig. 6 is a graph showing part of the waveform amplitudes of the first and second
detection signals obtained from the rotation detecting section of the rotational angle
detecting device shown in Fig. 1.
[0032] Fig. 7 shows the relationship between the angle of rotation of the steering wheel
and the output voltages of the first to third detection signals.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0033] Hereunder, a description of embodiments of the present invention will be given with
reference to the drawings.
[0034] Fig. 1 is a structural view of the main portion of an embodiment of a rotational
angle detecting device in accordance with the present invention. The rotational angle
detecting device is used to detect the angle of rotation of the steering wheel of
an automobile.
[0035] As shown in Fig. 1, the rotational angle detecting device of the embodiment comprises
a rotation detecting section 1, a controlling section (microcomputer) 2, a storage
section (memory) 3, a controller 4, a mechanism 5 to be controlled, and a bus line
6 for a local area network (LAN). A steering shaft (not shown) of an automobile is
connected to the rotation detecting section 1. The mechanism 5 to be controlled comprises
an automobile suspension mechanism and an automatic transmission mechanism.
[0036] Here, the rotation detecting section 1 is connected to the controlling section 2.
The controlling section 2 is connected to the controller 4 through the LAN bus line
6, and to the storage section 3.
[0037] Figs. 2A and 2B are sectional views showing in detail the structure of a rotary sensor
which is the rotation detecting section 1. Fig. 2A is a horizontal sectional view,
and Fig. 2B is a sectional view taken along line IIB-IIB in Fig. 2A.
[0038] As shown in Figs. 2A and 2B, the rotary sensor comprises a housing 7, a rotor 8,
a rotary shaft 9, a bearing 10, a worm gear 11, a sliding member 12, a first magnet
13
1, a second magnet 13
2, a first Hall element 14
1, a second Hall element 14
2, a third Hall element 14
3, and a circuit board 15.
[0039] The housing 7 comprises a case 7A and a cover 7B. The housing 7 is formed by covering
an opening in the case 7A with the cover 7B. One annular protrusion 7C is formed at
the bottom portion of the case 7A. Similarly, one annular protrusion 7D is formed
at the inside surface of the cover 7B. The rotor 8 is drum-shaped. With the steering
shaft (not shown) of an automobile being inserted in the center opening of the rotor
8, the rotor 8 is secured to the steering shaft. The rotor 8 comprises a small-width
protrusion 8A formed at the center of the outer periphery thereof in the widthwise
direction and a worm 8B formed along the entire periphery of the protrusion 8A. When
the housing 7 is being formed, both outer peripheral edges of the rotor 8 are fitted
into the inner sides of the annular protrusions 7C and 7D, and, while the small-width
protrusion 8A protrudes externally from between the annular protrusions 7C and 7D,
the rotor 8 is rotatably stopped inside the housing 7. One end of the rotary shaft
9 is mounted to the case 7A through the bearing 10, while the other end is stopped
by the case 7A through a wave-shaped washer 10A. The rotary shaft 9 has a screw groove
formed along the outer periphery of a portion thereof which is fitted to the sliding
member 12 (described later). The worm gear 11 is fitted to the rotary shaft 9, and
engages the worm 8B. The worm gear 11 has a cylindrical magnet holding section 11A
connected thereto, and the first magnet 131 which is cylindrical in shape is fitted
to the periphery of the magnet holding portion 11A. Here, portions of the first magnet
13
1 opposing each other in the circumferential direction comprise the N pole and the
S pole. The sliding member 12 which is cylindrical in shape has a screw groove (not
shown) formed in the inner peripheral portion thereof which is fitted to the rotary
shaft 9. When the sliding member 12 is fitted to the rotary shaft 9, the screw grooves
of both the sliding member 12 and the rotary shaft 9 engage each other. A protruding
guiding portion (not shown) which is fitted to a guide groove (not shown) of the housing
7 is formed along the outer periphery of the sliding member 12 so as to prevent rotation
with the rotary shaft 9 which is rotating. In addition, the second magnet 13
2 which is rod-shaped is formed at the sliding member 12 in an axial direction of the
rotary shaft 9. Here, the opposing portions of the first magnet 13
1 in the circumferential direction comprises a N pole and a S pole. One end of the
second magnet 13
2 is the N pole, and the other end of the second magnet 13
2 is the S pole. The first Hall element 14
1 and the second Hall element 14
2 are mounted to the circuit board 15 so as to be disposed near the cylindrical first
magnet 13
1 at an angle of 90 degrees from the axial core of the rotary shaft 9. The third Hall
element 14
3 is mounted to the circuit board 15 so as to be close to the rod-shaped second magnet
13
2. When the housing 7 is being formed, both ends of the circuit board 15 is held inside
the housing 7 by a board holding section (no reference numeral).
[0040] In the above-described structure, the housing 7 and the circuit board 15 are base
members, while the rotor 8, the rotary shaft 9, etc., together form a rotor structure.
[0041] Figs. 3 to 5 are graphs showing the waveforms of detection signals output from the
rotary sensor shown in Figs. 2A and 2B when the steering wheel of an automobile is
rotated. More specifically, Fig. 3 is a graph showing the waveforms of first and second
detection signals. Fig. 4 is a graph showing the waveform of a third detection signal.
Fig. 5 is a graph showing the waveforms of the first to third detection signals. In
Figs. 3 to 5, the horizontal axis represents the angle of rotation of the steering
wheel, while the vertical axis represents the voltage values (that is, the amplitudes)
of the detection signals.
[0042] With reference to the structural views of Figs. 1, 2A, and 2B, and the graph of Fig.
3 showing the signal waveforms, the operation of a first embodiment of the rotational
angle detecting device in accordance with the present invention used to create detection
information using the first and second detection signals will be given.
[0043] In the rotation detection section 1, when the steering wheel of an automobile is
rotated in order to rotate a steering shaft connected to the steering wheel, the rotor
8 having the steering shaft inserted therein is rotated. The rotation of the rotor
8 causes the worm gear 11 engaging the worm 8B of the rotor 8 and the rotary shaft
9 to which the worm gear 11 is mounted to rotate at the same time. The rotation of
the worm gear 11 causes the magnet holding section 11A connected to the worm gear
11 and the first magnet 13
1 mounted to the magnet holding section 11A to rotate at the same time. When the first
magnet 13
1 rotates, the distance between the N and S poles of the first magnet 13
1 and the first and second Hall elements 14
1 and 14
2, both of which are mounted close to the first magnet 13
1, to change periodically. As shown in Fig. 3, the first and second detection signals
a and b which have the same amplitudes and periods and which are out of phase by 1/4
wavelength are output from the first and second Hall elements 14
1 and 14
2. The first and second detection signals a and b output from the rotation detecting
section 1 are supplied to the controlling section 2.
[0044] As shown in Fig. 3, in the embodiment, the first and second detection signals a and
be output from the rotation detecting section 1 have peak-to-peak amplitudes voltages
of 4.0 V, have periods which correspond to 90° in terms of the angle of rotation of
the steering wheel, and are out of phase by 1/4 wavelength, which is 22.5° in terms
of the angle of rotation of the steering wheel.
[0045] From its neutral position (when its angle of rotation is 0°), the steering wheel
of an automobile can usually rotate two times (which corresponds to an angle of rotation
of +720°) in one direction towards the right, and two times (which corresponds to
an angle of rotation of -720°) in the other direction towards the left. In the rotation
detecting section 1, the angle of rotation of the steering wheel (that is, the steering
shaft) is required to be in the range of ±720° from the neutral position, which is
a total of 1440°. In this case, since the rotation detecting section 1 periodically
obtains the aforementioned first and second detection signals a and b within the entire
rotational angle range of 1440° of the steering wheel, it can usually measure all
of the rotational angles of the steering wheel.
[0046] The most recent first and second detection signals a and b which have been output
from the rotation detecting section 1 are supplied to the controlling section 2.
[0047] Here, based on the most recent first and second detection signals a and b which have
been supplied, the controlling section 2 performs the following operations.
[0048] The controlling section 2 compares in a previously determined period the amplitudes
(that is, voltage values) of the most recent first and second detection signals a
and b which have been supplied in order to determine whether or not their amplitudes
are within proper ranges during the comparison.
[0049] Fig. 6 is a graph showing part of the waveform amplitudes of the first and second
detection signals a and b obtained from the rotation detecting section 1. It is used
to illustrate their states when their amplitudes are being compared.
[0050] In Fig. 6, A° represents the angle of rotation of the steering wheel representing
one determination timing point when determining the amplitudes of the corresponding
first and second detection signals a and b. The areas within the dotted lines which
are drawn above and below the first and second detection signals a and b so as to
be parallel thereto represent detection errors (tolerances) of the amplitudes of the
first and second detection signals a and b. Ordinarily, these areas are set within
ranges of ±0.1 V with respect to corresponding amplitude values.
[0051] Using Fig. 6 which illustrates part of the waveforms of the first and second detection
signals a and b, the operations performed by the controlling section 2 when determining
whether or not the amplitudes of the corresponding first and second detection signals
a and b fall within their proper ranges will be described.
[0052] The controlling section 2 previously finds out the amplitude values of the first
and second detection signals a and b at the determination timing point. In Fig. 6,
at the determination timing point A°, the amplitude value of the first detection signal
a is 4.0 V, while the amplitude value of the second detection signal 6 is 3.0 V.
[0053] Taking into consideration an error (of ± 0.1 V) in the detection of the amplitude
value of the first detection signal a and an error (of ± 0.1 V) in the detection of
the amplitude value of the second detection signal b when the amplitude value of the
first detection signal a and the amplitude value of the second detection signal b
at the determination timing point A° are obtained, the controlling section 2 determines
that the amplitude values of the corresponding first and second detection signals
a and b are within the proper ranges when the amplitude value of the second detection
signal b falls within a range of 3.0 ± 0.2 V and the amplitude value of the first
detection signal falls within a range of 4.0 ± 0.2 V in the case where the amplitude
value of the first detection signal a is 4.0 V and the amplitude value of the second
detection signal b is 3.0 V.
[0054] When the controlling section 2 determines that the amplitude values of the corresponding
first and second detection signals a and b fall within their proper ranges, it sends
the most recent first and second detection signals and b to the storage section 3.
The most recent first and second detection signals a and b are written over the first
and second detection signals a and b which have been previously stored in the storage
section 3 in order to update the storage content of the storage section to the most
recent first and second detection signals a and b.
[0055] Thereafter, using the most recent first and second detection signals a and b, the
controlling section 2 detects the direction and angle of rotation of the steering
wheel, and creates detection information of the detected rotational direction and
the angle of rotation of the steering wheel from its neutral position. The created
detection information is supplied to the controller 4 through the LAN bus line 6.
Based on the supplied detection information, the controller 4 carefully executes a
controlling operation on the mechanism 5 to be controlled, such as the automatic transmission
and the suspension of the automobile.
[0056] Referring to Figs. 1, and 2A and 2B which are structural views, and Figs. 3 to 5
which illustrate the signal waveforms, a description of the operation of a second
embodiment of a rotational angle detecting device in accordance with the present invention
which creates detection information using a third detection signal c in addition to
the first and second detection signals a and b will be given.
[0057] As in the operation of the first embodiment, when the steering wheel of an automobile
rotates, causing a steering shaft connected to the steering wheel to rotate, first
and second detection signals a and b having the same amplitudes and periods and being
out of phase by 1/4 wavelength are output from a first Hall element 14
1 and a second Hall element 14
2 in a rotation detecting section 1, as shown in Fig. 3. At the same time, when a rotary
shaft 9 rotates, a sliding member 12 whose screw gear engages the rotary shaft 9 slides
in the axial direction of the rotary shaft 9, causing a second magnet 13
2 mounted to the sliding member 12 to also slide in the axial direction of the rotary
shaft 9. When the second magnet 13
2 slides, the distance between the N and S poles of the second magnet 13
2 and a third Hall element 14
3 changes, so that the third detection signal c which increases (or decreases) linearly
as the angle of rotation of the steering wheel changes in one period is output from
the third Hall element 14
3 as shown in Fig. 4. The first to third detection signals a to c output from the rotation
detecting section 1 are supplied to a controlling section 2.
[0058] In the second embodiment, as shown in Figs. 3 to 5, the first and section detection
signals a and b output from the rotation detecting section 1 have peak-to-peak amplitude
voltages of 4.0 V, have periods corresponding to 90° in terms of the angle of rotation
of the steering wheel, and are out of phase by 1/4 wavelength, which is 22.5° in terms
of the angle of rotation of the steering wheel. Similarly, as shown in Figs. 4 and
5, the third detection signal c output from the rotation detecting section 1 has a
minimum amplitude of 0.5 V and a maximum amplitude of 4.5 V, and a period corresponding
to 1440° in terms of the angle of rotation of the steering wheel. Here, since, as
mentioned previously, the rotation detecting section 1 previously obtains the first
to third detection signals a to c within the entire rotational angle range of 1440°
of the steering wheel, the rotation detecting section 1 is ordinarily capable of detecting
all rotational angles of the steering wheel.
[0059] The most recent first to third detection signals a to c output from the rotation
detecting section 1 are supplied to the controlling section 2. Based on the most recent
first to third detection signals a to c which have been supplied, the controlling
section 2 performs the following operations.
[0060] As in the first embodiment, the controlling section 2 compares in a previously determined
period the amplitudes (that is, the voltage values) of the most recent first and second
detection signals a and b which have been supplied in order to determine whether or
not the amplitude values of the first and second detection signals a and b fall within
their proper ranges. More specifically, the controlling section 2 determines that
the amplitude values of the first and second detection signals a and b fall within
their proper ranges when the amplitude value of the second detection signal b falls
within the range of 3.0 ± 0.2 V and the amplitude value of the first detection signal
a falls within the range of 4.0 ± 0.2 V in the case where the amplitude value of the
first detection signal a is 4.0 V and the amplitude value of the second detection
signal b is 3.0 V. Otherwise, the controlling section 2 determines that the amplitude
values of the corresponding first and second detection signals a and b do not fall
within their proper ranges.
[0061] Here again, when the controlling section 2 determines that the amplitude values of
the corresponding first and second detection signals fall within their proper ranges,
it sends the most recent first and second detection signals a and b which have been
supplied to a storage section 3. The most recent first and second detection signals
a and b are written over the first and second detection signals a and b which have
been previously stored in the storage section 3 in order to update the storage content
of the storage section 3 to the most recent first and second detection signals a and
b.
[0062] Then, the controlling section 2 compares the amplitude values of the corresponding
most recent first and second detection signals a and b with the amplitude value of
the most recent third detection signal c in order to determine whether or not they
fall within their proper ranges.
[0063] Here, as shown in Fig. 4, the amplitude value of the most recent third detection
signal c which is compared to the amplitude values of the corresponding most recent
first and second detection signals a and b varies with the rotational angle location
of the steering wheel. Therefore, in the second embodiment illustrated in Figs. 3
to 5, when the angle of rotation of the steering wheel is 0° (which corresponds to
its neutral position), the amplitude value is 2.5 V. When the angle of rotation of
the steering wheel is equal to either one of the extreme values of the rotational
angle range, the amplitude value is a minimum at 0.5 V or is a maximum at 4.5 V. When
the angle of rotation of the steering wheel is between these extreme values, the amplitude
value varies linearly between 0.5 V and 4.5 V.
[0064] When the controlling section 2 compares the amplitude values of the corresponding
first and second detection signals a and b with the amplitude value of the most recent
third detection signal c, and determines that these amplitude values fall within their
proper ranges, it sends the most recent third detection signal c which has been supplied
to the storage section 3. The most recent third detection signal c is written over
the third detection signal c which has been previously stored in the storage section
3 in order to update the storage content of the storage section 3 to the most recent
third detection signal c in addition to updating the storage content of the storage
section 3 to the most recent first and second detection signals a and b.
[0065] Thereafter, using each of the most recent first to third detection signals a to c,
the controlling section 2 detects the direction and angle of rotation of the steering
wheel, and creates detection information of the detected direction of rotation and
the angle of rotation of the steering wheel from the neutral position. The created
detection information is supplied to a controller 4 through a LAN bus line 6.
[0066] On the other hand, when the controlling section 2 compares the amplitude values of
the first and second detection signals a and b with the amplitude value of the third
detection signal c, and determines that the amplitude values thereof do not fall within
their proper ranges, the most recent third detection signal c is destroyed so that
it is not sent to the storage section 3. At the same time, the immediately previously
stored third detection signal c is read out from the storage section 3.
[0067] In the second embodiment, the period (that is, the sampling period) of the output
of the third detection signal c from the rotation detecting section 1 is 200 µsec,
and the period (that is, the transmission period) of the output of the detection information
from the controlling section 2 is 5 ± 0.5 msec (10 ± 1 msec). Since it is necessary
to use the immediately previously stored third detection signal c when the amplitude
value of the most recent third detection signal c does not fall within its proper
range, the sampling period and the transmission period are set asynchronously. In
order to increase precision, the controlling section 2 sets a high order of priority
for an interruption in the sampling period than in the transmission period. When the
setting is such, the transmission period may vary, but the controlling section 2 is
designed so that most of the variations fall within the target range of 5 msec.
[0068] Thereafter, using the most recent first and second detection signals a and b and
the third detection signal c read out from the storage section 3, the controlling
section 2 detects the direction of rotation and angle of rotation of the steering
wheel, and creates detection information of the detected direction of rotation of
the steering wheel and angle of rotation of the steering wheel from its neutral position.
The created detection information is supplied to the controller 4 through the LAN
bus line 6.
[0069] Based on the supplied detection information, the controller 4 carefully controls
a mechanism 5 to be controlled, such as the automatic transmission and the suspension
of the automobile.
[0070] In the second embodiment, the detection operations of the rough rotational angle
and rotational direction of the steering wheel carried out at the controlling section
2 using the third detection signal c are the same as the detection operations of the
rough rotational angle and rotational direction of the steering wheel by the previously
described, already proposed rotation-side sensor using the graph of Fig. 7. In addition,
the detection operation of the very small rotational angle using the first and second
detection signals a and b carried out at the controlling section 2 is the same as
the detection operation of the very small rotational angle of the steering wheel by
the previously described, already proposed rotation-side sensor using the graph of
Fig. 7. Therefore, the detection operations of the rotational direction, the rough
rotational angle, and the very small rotational angle in the second embodiment will
not be described any further.
[0071] Even in the second embodiment, when the controlling section 2 determines that the
amplitude values of the most recent first and/or second detection signals a and b
do not fall within their proper ranges, the controlling section 2 determines that
either one or both of the most recent first and second detection signals a and b which
have been supplied is or are an unsuitable detection signal or unsuitable detection
signals, and gets rid of the most recent first and/or second detection signals a and
b so that they are not sent to the storage section 3. When the most recent first and
second detection signals a and b are destroyed, the controlling section 2 does not
transmit the most recent third detection signal c which is compared therewith to the
storage section 3 and gets rid of it.
[0072] At this point of time, the controlling section 2 does not create detection information
so that no detection information is supplied to the controller 4 through the LAN bus
line 6. Therefore, the mechanism 5 to be controlled is not controlled by the controller
4.
[0073] As can be understood from the foregoing description, in the first aspect of the invention,
the first and second detection signals output from the rotation detecting section
are transmitted to the storage section, are updated, and stored in the storage section.
The controlling section cyclically compares the most recent first and second detection
signals output from the rotation detecting section at the determined period. When
it determines that at least one of the most recent first and second detection signals
is not a proper detection signal, an angle signal based on the most recent first detection
signal and second detection signal is not supplied to the controller. Therefore, an
improper piece of detection information which is created based on the improper detection
signal is not supplied to the controller, so that, at all times, the controller can
properly perform a controlling operation to operate a fail-safe structure, making
it possible to obtain a highly reliable rotational angle detecting device.
[0074] According to the second aspect of the invention, the first to third detection signals
output from the rotation detecting section are transmitted to the storage section,
are updated, and stored in the storage section. The controlling section first cyclically
compares the most recent first and second detection signals output from the rotation
detecting section at the determined period. When the controlling section determines
that both of the most recent first and second detection signals are proper detection
signals, it cyclically compares the most recent third detection signal output from
the rotation detecting section with the most recent first and second detection signals
in a similarly determined period. When the controlling section determines that the
third detection signal is an improper detection signal, it creates a proper piece
of detection information using the most recent first and second detection signals
and the third detection signal immediately previously read out from the storage section.
Since this detection information is supplied to the controller, an improper piece
of detection information which is created based on any improper detection signal is
not supplied to the controller. Therefore, the controller can at all times perform
a proper controlling operation to operate a fail-safe mechanism. Using the detection
information based on the first to third detection signals, it is possible to obtain
a rotational angle detecting device which is more reliable than the rotational angle
detecting device of the first aspect of the invention.